They already did the "Which is the best penetrant" test and ATF/Acetone beat out Kroil and all the the rest. PB Blaster is a grease disolver. Not sure why people think it's a rust buster.
We've been there and I've been using Ed's Red (sans lanolin) to soak rusty stuff. Not enough data to report on.
OK, the truth: I like the Kroil can. It fits my MTM rifle cradle and I can dispense tiny doses without wasting a bunch of it and I like the smell dammit.
Even though I start soaking "planned" projects a week in advance by dousing what rusty stuff needs removed, NOTHING seems to ever soak all the way to the trouble-spot and sheer brute force (or applied physics in the manner of mechanical advantage) is what always seems to do the trick. Kroil, PB-Blaster, Free-All, Ben's Red - doesn't matter. In all honesty, I use PB-Blaster where gravity betrays me and won't let me drip my Kroil. 98% of PB-Blaster is wasted going everywhere but where it should. I can drip Ed's Red anywhere I can drip Kroil, but PB-Blaster shoots uphill.
No lyin' - What I use for freeing rusty stuff is more about which one I can apply to the troubled area and I almost always have to unstick something stuck well before any of the above get to the trouble-spot.
But, for cleaning cast-bullet guns, any of the above does it.
I hate the smell of PB-Blaster. Sometimes it's the only thing I can reach rusty stuff with though.